1. Preheat oven to 350 degrees F. Chop the butter and marzipan to make them easier to break down, and put them in the bowl of the food processor, fitted with the metal blade, with the sugar. Process until combined and pretty well smooth. Add almond and vanilla extracts, process again, then break the eggs one at a time through the funnel, processing again each time. Mix the flour and tip down the funnel, processing yet again, and then pour the mixture into the prepared pan, scraping the sides and bottom of the bowl with a rubber spatula.

2. Bake for 50 minutes, but check from 40. Then, when the cake looks golden and cooked and a cake tester or fine skewer (or a piece of spaghetti) comes out cleanish, remove from the oven and leave to cool in the pan before using turning out. (This is when you will be feeling grateful if it's the springform you're using.)